C(sp2)–H Functionalization of Imidazole at the C2- and C4-Position via Palladium-Catalyzed Isocyanide Insertion Leading to Indeno[1,2‑d]imidazole and Imidazo[1,2‑a]indole Derivatives

An efficient strategy for the construction of fused imidazole derivatives through a palladium-catalyzed isocyanide insertion reaction has been accomplished. The methodology provides an operationally simple and versatile route for the synthesis of indeno­[1,2-d]­imidazole and imidazo­[1,2-a]­indole skeletons which are rarely reported. The key features of the protocol are construction of sequential C–C/C–C/C–N bonds via C­(sp2)–H functionalization of imidazole at the C2- and C4-position, respectively. The compounds can be synthesized with diverse scaffolds, easily accessible starting materials, and moderate to good yields.